Conventional vehicle lights can employ a resin molding for reasons and benefits in view of heat resistance, weather resistance, optical characteristics and the like. Such a resin molding may include a housing formed from a light-absorbing resin using acrylonitrile styrene acrylate (ASA) and the like and can also be imparted with a light absorbing property. A lens can be included that is formed from a light-transmitting resin such as a polymethylmethacrylate (PMMA) or a polycarbonate and is welded to the housing.
Japanese Patent Application Laid-Open No. 2000-294013 (corresponding to Japanese Patent No. 3973792, and U.S. Pat. No. 6,592,239B1) discloses a vehicle light in which a lens and a lamp body (housing) are welded. In this vehicle light, the lens is pressed against the lamp body, and in this state, a laser beam is allowed to be incident on and pass through the transparent lens. The passing beam can be incident on the lamp body surface that is in contact with the lens while being pressed to heat and fuse the lamp body surface. The fusing heat in the lamp body surface can be transferred to the ends of the seal support legs of the lens. The technique disclosed in this publication proposes the scanning with a laser beam along the entire circumference of the lens to integrate the lens and the lamp body together. In this technique, the lamp body is provided with a positioning groove for preventing the seal support legs of the lens from becoming displaced. Accordingly, the lens and the lamp body can be laser-welded while the physical relationship therebetween can be maintained by the groove and legs. Furthermore, even if a slight bun is generated, it can be confined within the positioning groove.
The technique disclosed in Japanese Patent Application Laid-Open No. 2001-243811 (corresponding to U.S. Pat. No. 6,464,374B2) is similar to the technique disclosed in Japanese Patent Application Laid-Open No. 2000-294013. The basic welding method disclosed in the previous publication is improved by the proposed method in which the bonded surface is inclined so that the laser beam can be obliquely incident on that surface. During the irradiation, a transparent plate is placed on the surface of a lens employed in the disclosed system, thereby reducing the light refraction effect to eliminate the condensing of light. Therefore, the light can reach the entire surface of the welded bonding surface to improve the bonding strength.
However, a method of welding a resin molding using a laser beam has not been fully developed as of yet in terms of sufficient bonding strength, simplicity of the process, and the like.
Further developments relating to a welding method have been performed in order to solve or at least address the above characteristics, features, and problems for a vehicle light having a lens and a housing that are welded together. Japanese Patent Application Laid-Open No. Hei 10-310676 discloses a resin composition for molding housings. This technique can utilize a resin composition for molding a housing to suppress the stringing phenomenon of the molten resin during welding of the housing that is thus molded.
Japanese Patent Application Laid-Open No. 2004-349123 discloses a welding method of heating and welding a housing and a lens without optical loss of the welding laser beam. Therein, an elastic light guiding member capable of conforming to the lens shape and a flat transparent base material can be disposed on the lens surface. In this state, a compression load is applied to bring the elastic light guiding member and the lens into close contact with each other. In this technique, the used members are selected to have the same or substantially same refractive index as those of the other members, so that the optical loss due to refraction or the like may be suppressed. In this way, the laser beam heating and welding can be facilitated.
Further, a typical vehicle light may have a housing with an inner surface subjected to aluminum deposition so that the inner surface of the housing can serve as a light reflecting surface. When such a light reflecting film, like an Al film, is deposited on a portion of the molded housing that is to be welded (sealed), the welding laser beam may be reflected thereon in a normal laser welding condition, resulting in welding failure. To cope with this characteristics/problem, a mask can be applied onto the welding portion of the housing before the Al deposition process so that the light reflecting film is prevented from being formed on the welding portion during the laser welding.
When a mask is provided onto the welding surface of the welding portion of the housing during the formation of a light reflecting film on the inner surface of the housing, the dedicated step for providing a mask onto a required area (masking process) is typically added, thereby increasing the manufacturing cost. In this case, when the mask is inaccurately provided or a masking treatment fails, aluminum may scatter and adhere to the welding surface of the housing.